Field of the Disclosure
Exemplary embodiments of the present disclosure relate to a supercritical CO2 power generating system for preventing cold-end corrosion, and more particularly, to such a system capable of improving reliability against cold-end corrosion by including a recirculation pump.
Description of the Related Art
As the need for efficient power production increases, and as the move toward decreasing the emission of pollutants (e.g., greenhouse gases) goes global, there have been several active efforts to increase power production while decreasing emissions. As an example of one such effort, there is the research and development of a power generating system using supercritical CO2 as a working fluid.
Supercritical CO2 has a similar density to a liquid-state fluid and a similar viscosity to other gases, so it is possible to miniaturize a power generation device and significantly decrease the power consumption required for compression and circulation of a fluid. At the same time, supercritical CO2 having a critical point at 31.4° C. and 72.8 atm, which is much lower than that of water having a critical point at 373.95° C. and 217.7 atm, may be relatively easily handled. In addition, power generating systems using supercritical CO2 are mostly operated as a closed cycle, in which the carbon dioxide used for power generation is not emitted to the outside, and thus can greatly contribute to reducing a country's emission of greenhouse gases.
However, beyond a certain scale, it is difficult to increase the capacity of existing power generating systems using supercritical CO2, such that goals for increased power can only be partial met. In the case of coal-fired power generation, it is particularly necessary to reduce emissions while increasing the power generation efficiency.
U.S. Patent Publication No. 2014-0102098 discloses a method to increase the efficiency of a supercritical CO2 power generating system, by additionally supplying heat to a working fluid using an external heat exchanger capable of recovering waste heat such as exhaust gas discharged from a boiler of a thermal power plant. However, there is an inherent problem with such external heat exchangers.
Generally, upon exchanging heat with waste heat gas, if the temperature of a cold-side working fluid of the external heat exchanger is lower than the dewpoint of sulfuric acid contained in the waste heat gas, water may condense on the high-temperature-side, i.e., the side into which the waste heat gas is introduced. Water condensation may lead to corrosion when condensed water droplets adhere to and accumulate in a metal tube of the external heat exchanger. This corrosion phenomenon is called cold-end corrosion.
Cold-end corrosion shortens the lifetime of the external heat exchanger and lowers its reliability, and in turn, lowers the overall reliability of the supercritical CO2 power generating system. Therefore, a method for solving these problems is needed.